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Radioligand Therapy

What is a Radioligand Therapy?

In radioligand therapies the radiopharmaceuticals (usually labeled with a beta-emitter such as lutetium-177) specifically bind to a tumoral target structure (usually a surface molecule).

Radioligand therapies are well-tolerated systemic therapies used in metastasized disease. The radiopharmaceutical is infused or injected into a peripheral vein.

Which tumor entities can be addressed?

a) For the treatment of well to moderately differentiated neuroendocrine tumors (NET) peptides targeting the somatostatin-receptor (SSTR) are used. In NET, radioligand therapy (also known as PRRT - peptide-receptor radionuclide therapy) is well-established and may achieve high rates of long lasting tumor remission and stabilization.

b) A relatively novel radioligand therapy is available for metastasized prostate cancer: Here a radioligand is used which specifically binds to the so-called prostate-specific membrane antigen (PSMA), that is overexpressed in prostate cancer. According to current, still preliminary data, the therapy may achieve a high rate of tumor response even in patients refractory to conventional chemotherapy.

How is the therapy performed?

The radiopharmaceutical is administered on the first day on our ward. Due to radiation protection legislations and also in order to estimate undesired radiation doses to critical organs (such as the kidney or bone marrow), the patient remains on our ward for approx. 4 days during which daily dosimetric studies are performed.

How often is the therapy performed?

The therapy consists of several applications (cycles) of therapy in intervals of 2-3 months: In case of NET-treatment with the radioligand Lutetium-177-DOTATATE, approx. 4-6 cycles will be delivered. For treatment of prostate cancer, usually 2-4 cycles are done. The number of cycles also depends on response to therapy, patient tolerability and estimated doses to the critical organs.

What are the side effects?

Since the injected pharmaceutical dose is very low, these substances are very well tolerated. Cumulative radiation doses to the critical organs are usually well below the radiation thresholds reported in the literature. However, the individual history of the patient (e.g. previous lines of chemotherapy) and other patient-specific data (e.g. laboratory findings) have to be respected.

What are the prerequisites?

Apart from the histological diagnosis of either a NET or prostate cancer, a sufficiently high expression of the target molecule (SSTR and PSMA, respectively) must be proven beforehand via a dedicated SSTR- or PSMA-ligand PET/CT-examination, respectively (so-called theranostic principle).

Moreover, a sufficient function of critical organs (e.g. adequate blood count and renal function) is mandatory.